clocksource: add samsung pwm timer driver

This adds a new clocksource driver for the PWM timer that is
present in most Samsung SoCs, based on the existing driver in
arch/arm/plat-samsung/samsung-time.c and many changes implemented by
Tomasz Figa.

Originally, the conversion of all Samsung machines to the new driver was
planned for 3.10, but that work ended up being too late and too invasive
just before the merge window.

Unfortunately, other changes in the Exynos platform resulted in some
Exynos4 setups, particularly the Universal C210 board to be broken. In
order to fix that with minimum risk, so we now leave the existing pwm
clocksource driver in place for all older platforms and use the new
driver only for device tree enabled boards. This way, we can get the
broken machines running again using DT descriptions.

All clocksource changes were implemented by Tomasz, while the DT
registration was rewritten by Arnd.

Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Cc: Tomasz Figa <t.figa@samsung.com>
Cc: Kyungmin Park <kyungmin.park@samsung.com>
Cc: Kukjin Kim <kgene.kim@samsung.com>
Cc: Ben Dooks <ben-linux@fluff.org>
Cc: John Stultz <john.stultz@linaro.org>
Cc: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 10 insertions, 0 deletions

diff --git a/drivers/clocksource/Kconfig b/drivers/clocksource/Kconfig
index e507ab7df60b..03caba2540e2 100644
--- a/drivers/clocksource/Kconfig
+++ b/drivers/clocksource/Kconfig
@@ -67,3 +67,13 @@ config CLKSRC_METAG_GENERIC
 	def_bool y if METAG
 	help
 	  This option enables support for the Meta per-thread timers.
+
+config CLKSRC_SAMSUNG_PWM
+	def_bool ARCH_EXYNOS4
+	depends on OF
+	select CLKSRC_MMIO
+	help
+	  This is a new clocksource driver for the PWM timer found in
+	  Samsung S3C, S5P and Exynos SoCs, replacing an earlier driver
+	  for all devicetree enabled platforms. This driver will be
+	  needed only on systems that do not have the Exynos MCT available.